This invention relates to a digital data communications system, and more particularly to a system comprising a master station and a plurality of slave stations connected to the master station over a digital link.
The invention finds application in a number of environments with distributed processing, for example in short-loop applications, such as PBX or in optical-fibber distributed systems. In such systems there is a need to provide multiple access to the slave stations while optimizing the use of available bandwidth, which may be limited. The data can be in any form of digital data, including digitized voice signals.
In an ISDN data transmission system, ranges of up to 4 kilometers on a twisted pair subscriber loop can be achieved using echo cancellation techniques at a subscriber data rate of 144 kbps (2B+D channels). An echo cancellation technique, however, is not easy to implement in a point to multipoint (multidrop) configuration.